1. Field of the Invention
The present invention relates to electrophotographic apparatus and more particularly to structure for establishing a reference potential (e.g. ground potential) on the photoconductor image member of such apparatus.
2. Description of the Prior Art
The photoconductor image members of electrophotographic apparatus generally include a photoconductive insulator layer overlying a conductive surface. One common image member type is in the form of an electrically conductive drum having an inorganic photoconductor surface, and the establishment of reference potential (e.g. by grounding the drum) presents no difficulties. However, it is becoming increasingly popular to form the photoconductor image member as a film which includes a conductive layer sandwiched between an electrically insulative support and an organic photoconductive insulator layer. With this image member configuration it is more difficult to establish reference potential because the conductive layer is not readily accessible for electrical contact.
Many alternative approaches have been developed for grounding such film-type photoconductor image members. The desirability of a particular one of the approaches for a given apparatus application depends significantly upon factors such as the photoconductor film format (e.g. sheet, web or endless belt), the degree of quality required and whether the photoconductor film is to be reused. For example, U.S. Pat. No. 4,344,698 discloses a useful technique for grounding a non-reusable photoconductor film web that moves through process stations, between a supply and take-up roll. The '698 moving contact grounding approach is to cut through the edge of the successive photoconductor layer portions so that underlying conductive layer portions are contacted by the grounded cutting blade. U.S. Pat. Nos. 3,533,692 and 3,552,957 disclose a fixed-contact grounding approach for film-type image members in sheet format, which involves attaching electrically conductive clamps, straps or rivets to an exposed portion of a conductive interlayer. U.S. Pat. No. 4,120,720 discloses another fixed-contact approach for sheet format film. In that approach holes are cut through the cross-section of the sheet and treated with conductive laquer to enable subsequent contact with an electrically conductive grounding pin of electrophotographic apparatus.
The prior art fixed-contact grounding approaches require special fabrication procedures, and this adds cost. It therefore would be desirable to have a simpler approach (e.g. similar to the cutting technique disclosed in the '698 patent) for the fixed-contact grounding of film-type image members in sheet format.